During the operation of an internal combustion engine a small portion of the air-fuel mixture inside the combustion chamber passes by the piston and piston rings into the crankcase just before combustion occurs. In like manner, exhaust fumes are forced past the piston rings into the crankcase just after combustion takes place. Collectively, these gases are termed blow-by, approximately 80% of which is unburned air-fuel mixture and 20% of which is a combustion product including water vapor, carbon dioxide and carbon monoxide.
Blow-by gases have always been a problem since, if they are allowed to remain in the crankcase, they form various deposits, acids and sludge, all of which are harmful to engine life and performance.
Traditionally, these fumes were vented to the atmosphere through a road draft tube. In recent years, however, the smog problem has created a need for preventing crankcase vapors from discharging into the atmosphere. As a consequence, positive crankcase ventilation (PCV) systems have been developed which recycle the engine blow-by gases back into the air-fuel induction system of the engine, thence into the combustion chambers where the hydrocarbons can be burned.
In order to maintan combustion efficiency during idling, deceleration, acceleration and cruising, a flow control valve is interposed in the conduit conducting the blow-by gases from the crankcase to the intake manifold. The flow control valve, termed a PCV valve, is ordinarily modulated either by the extent of the pressure, or vacuum, in the crankcase or by the amount of vacuum in the intake manifold.
So long as the PCV valve works properly, the system serves its purpose in an effective manner. In fact, increased mileage is afforded by the return of unburned fuel to the combustion chambers of the engine.
Unfortunately, however, the PCV valve, which meters the flow of the crankcase emissions, often becomes clogged. When the valve sticks in one position, excessive air flow can unbalance the engine's air-fuel ratio, thus causing rough idling or even stalling. If the valve sticks in the other position, there is too little flow. In this situation the fumes will not be carried off and the crankcase will become contaminated with sludge, acid, and other harmful products which lead to engine corrosion, poor lubrication and eventual serious engine damage if the valve is not cleaned or replaced.
Clogging of the PCV valve frequently occurs since the crankcase emissions not only comprise air and blow-by, both of which pass harmlessly through the valve, but also water in both liquid and vapor phase, resins, varnishes and acids, as well as products of a carbonaceous and calcareous nature, the latter having its source in lubrication additives. Solids, such as soot and various oxidation products, are also present and further tend to interfere with the operation of the PCV valve.
In order to maintain the PCV valve and engine in good operating condition, it is desirable to separate out and collect these harmful fractions found in the crankcase emissions while permitting the harmless unburned gaseous hydrocarbons and air to continue on through the PCV valve, thence to the intake manifold.
The market place as well as the patent literature provide several types of devices which remove at least some of the deleterious components found in crankcase emissions and which also allow the harmless fraction to pass through.
A crankcase emission liquid collector is disclosed, for example, in U.S. Pat. No. 3,250,062 to H. F. Lusk. In this patent, centrifuging and expansion are utilized to effect separation.
There remains, however, considerable room for improvement.